Endoscopic surgical instruments are often preferred over traditional open surgical devices because a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Positioning the end effector is constrained by the trocar. Generally, these endoscopic surgical instruments include a long shaft between the end effector and a handle portion manipulated by the clinician. This long shaft enables insertion to a desired depth and rotation about the longitudinal axis of the shaft, thereby positioning the end effector to a degree. With judicious placement of the trocar and use of graspers, for instance, through another trocar, often this amount of positioning is sufficient. Surgical stapling and severing instruments, such as described in U.S. Pat. No. 5,465,895 to Knodel et al., are an example of an endoscopic surgical instrument that successfully positions an end effector by insertion and rotation.
One stapler manufactured by United States Surgical Corporation and described in U.S. Pat. Nos. 6,644,532 and 6,250,532 to Green et al. have an end effector that pivotally moves along a single plane in steps dependent upon activation of a lever that correspondingly moves along a single plane in similar steps. See FIGS. 31 and 32 therein. The U.S. Surgical Corp. stapler, however, is limited by the predetermined angles that it can achieve and by the limited side to side pivoting (−45 degrees to +45 degrees) that requires two hands for operation.
Depending upon the nature of the operation, it may be desirable to further adjust the positioning of the end effector of an endoscopic surgical instrument rather than being limited to insertion and rotation. In particular, it is often desirable to orient the end effector at an axis transverse to the longitudinal axis of the shaft of the instrument. The transverse movement of the end effector relative to the instrument shaft is conventionally referred to as “articulation.” This articulated positioning permits the clinician to more easily engage tissue in some instances. In addition, articulated positioning advantageously allows an endoscope to be positioned behind the end effector without being blocked by the instrument shaft.
While the aforementioned non-articulating stapling and severing instruments have great utility and may be successfully employed in many surgical procedures, it is desirable to enhance their operation with the ability to articulate the end effector, thereby giving greater clinical flexibility in their use. Articulating surgical instruments generally use one or more firing bars that move longitudinally within the instrument shaft and through the articulation joint to fire the staples from the cartridge and to cut the tissue between the innermost staple lines. One common problem with these surgical instruments is control of the firing bar through the articulation joint. At the articulation joint, the end effector is longitudinally spaced away from the shaft so that the edges of the shaft and end effector do not collide during articulation. This gap must be filled with support material or structure to prevent the firing bar from buckling out of the joint when the single or multiple firing bars is subjected to longitudinal firing loads. What is needed is a support structure that guides and supports the single or multiple firing bars through the articulation joint and bends or curves as the end effector is articulated.
U.S. Pat. No. 5,673,840 to Schulze et al. describes a flexible articulation joint that is formed from an elastomeric or plastic material that bends at the flexible joint or “flex neck.” The firing bars are supported and guided through a hollow tube within the flex neck. The flex neck is a portion of the jaw closure mechanism and moves longitudinally relative to the end effector, shaft, and firing bars when the jaws are closed on tissue. The firing bars then move longitudinally within the flex neck as the staples are fired and tissue is cut.
U.S. Pat. No. 5,797,537 to Oberlin et al. (owned by Richard-Allan Medical Industries, Inc.) describes an articulation joint that pivots around a pin, rather than bends around a flex joint. In this instrument, firing bars are supported between a pair of spaced support plates connected at one end to the shaft and at another end to the end effector. At least one of those connections is a slidable connection. The support plates extend through the articulation joint adjacent to the flexible drive member in the plane of articulation such that the support plates bend through the gap in the plane of articulation and the flexible firing bar bends against the support when the tip is articulated in one direction from its aligned position. U.S. Pat. No. 6,330,965 to Milliman et al. from U.S. Surgical teaches the use of support plates that are fixedly attached to the shaft and slidably attached to the end effector.
Although these known support plates guide a firing bar through an articulation joint, it is believed that performance may be enhanced. For instance, it is often desirable for the firing bar to be rapidly accelerated during firing to ensure sufficient momentum for severing tissue effectively. Rigidly attached support plates may tend to dislodge in response, allowing the firing bar to blow out from the articulation joint. As a further example, it is desirable for the instrument to operate in the same manner whether articulated or not. Increased friction when articulated would be inconvenient and distracting to the clinician if required to exert a varying amount of firing force.
Consequently, a significant need exists for an improved articulation mechanism for a surgical instrument mechanism that provides enhanced support to a firing bar through the articulation joint.
As mentioned above, as used in the art and as used herein, transverse movement of a medical end effector relative to an instrument shaft is conventionally referred to as “articulation.” In prior art medical devices having articulation control, the articulation movement is directed actively from the device handle. This active control can be mechanical and/or electrical. For example, some prior art devices have levers at the top of the control handle and, when pivoted left the end effector articulates left and when pivoted right the end effector articulates right. Some operate with opposite movement. To effect this articulation, it is very difficult for the operator to use only one hand. Thus, often, the operator must hold the handle with one hand and pivot the articulation lever with the other hand. As is known, the trend for laparoscopic and other similar medical devices is to make them operable with a single hand because surgeons often lose control of the device held in the second hand when it is necessary to remove their second hand from that device in order to operate the articulation lever. Loss of device control is undesirable and extends the surgical procedure if the device falls outside the view of the operating surgeon. One prior art device uses electrical measures to actively control articulation. In U.S. Pat. No. 7,213,736 to Wales et al., electrical power is supplied to an electrically actuated polymer to articulate the end effector actively in the desired direction. These prior art devices can be characterized by referring to them as “active articulation” devices, in which an articulation control device is present on the handle and extends through the articulation joint to force the articulation in either articulation direction. In other words, the forces required to perform articulation are generated internally in the device.
Thus, a significant need also exists for an improved articulation mechanism for a surgical instrument mechanism that is operable with only a single hand. The articulation assembly of the present invention has no mechanical control device in the handle to effect direct control of articulating movement of the end effector. There is no articulation control device present on the handle that extends through the articulation joint to force the end effector to articulate in a direction. Instead, articulation of the end effector is dependent upon pressure between a surface of the environment in which the end effector exists and an exterior surface of the end effector, for example, at a location distal of the articulation joint. A torque to pivot the inventive end effector about the articulation axis arises from forces external to the device. One force is present by the user holding the handle. The other force acts distal of the articulation joint and imparted by the environment in which the end effector is present and against which the end effector is being held. In other words, the forces required to perform articulation are external to the device. This motion can be referred to herein as “passive articulation” and the “articulation joint” of the present invention operates with passive articulation—it requires a torque external to the device to articulate the end effector about the axis of the passive articulation joint.